<!-- 这个文件中就是客户端的代码逻辑 -->

<!DOCTYPE html>
<html>
  <head>
    <meta name="viewport" content="width=device-width,initial-scale=1.0">
    <title>Socket.IO chat</title>
    <style>
      body { margin: 0; padding-bottom: 3rem; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; }

      #form { background: rgba(0, 0, 0, 0.15); padding: 0.25rem; position: fixed; bottom: 0; left: 0; right: 0; display: flex; height: 3rem; box-sizing: border-box; backdrop-filter: blur(10px); }
      #input { border: none; padding: 0 1rem; flex-grow: 1; border-radius: 2rem; margin: 0.25rem; }
      #input:focus { outline: none; }
      #form > button { background: #333; border: none; padding: 0 1rem; margin: 0.25rem; border-radius: 3px; outline: none; color: #fff; }

      #messages { list-style-type: none; margin: 0; padding: 0; }
      #messages > li { padding: 0.5rem 1rem; }
      #messages > li:nth-child(odd) { background: #efefef; }
    </style>
  </head>
  <body>
    <!-- 显示聊天消息 -->
    <ul id="messages"></ul>

    <!-- 输入聊天消息 -->
    <form id="form" action="">
      <input id="input" autocomplete="off" /><button>Send</button>
    </form>

    <!-- 客户端逻辑 -->
    <script src="/socket.io/socket.io.js"></script>
    <script>
      // 创建客户端套接字对象
      const socket = io();

      // 获取等操作的 DOM 元素
      const form = document.getElementById('form');
      const input = document.getElementById('input');
      const messages = document.getElementById('messages');

      // 表单提交事件处理: 向服务器发送消息
      form.addEventListener('submit', (e) => {
        // 阻止表单提交
        e.preventDefault();

        if (input.value) {
          // 触发一个事件，该事件是在服务端注册监听的
          // 用于从客户端向服务端发送消息
          socket.emit('onServerReceive', input.value);
          input.value = '';
        }
      });

      // 注册客户端这边的事件监听，用于接收服务端发送的消息
      socket.on('onClientReceive', (msg) => {
        const item = document.createElement('li');
        item.textContent = msg;
        messages.appendChild(item);
        window.scrollTo(0, document.body.scrollHeight);
      });
    </script>
  </body>
</html>